Snap or retaining rings are either "internal" or "external". The internal type of retaining ring is used to retain elements such as bearings or shafts, within a bore. In order to install the ring it is contracted to allow it to pass into the bore, and then allowed to expand for engagement with an internal groove formed around the bore. The external type of retaining ring is used to retain elements such as bearings, gears or pulleys on shafts. An external ring normally engages an annular groove formed in a shaft to inhibit axial movement of an element mounted on the shaft. An external ring is installed by expanding the ring until its internal diameter is greater than the shaft diameter.
The tools typically used for installing and removing internal and external rings are substantially different. A tool for installing and removing external rings, for example, must expand the ring to increase its internal diameter in order to accommodate the shaft. An internal ring installation and removal tool, however, must contract the ring in order to decrease its external diameter to enable the ring to pass through a bore. Since the function and performance required of such tools is so substantially different, retaining ring pliers are often supplied as single purpose "internal" and "external" tools. These single purpose pliers are intended for use only in installing or removing one type of retaining ring, and both types of pliers are therefore required in order to install or remove both external and internal types of retaining rings.
One solution to the provision of a tool suitable for either internal or external rings has been the provision of convertible tools capable of switching between internal and external positions. These required manipulation of interconnected pieces, movement of a linkage arrangement mounted on the tool or disassembly of jaw and/or handle sections in order to accomplish the conversion.
One such convertible tool, known as a universal plier, is illustrated in U.S. Pat. No. 4,625,379 issued Dec. 2, 1986 to J. E. C. Anderson. The tool includes a pair of pivotally interconnected handles and a pair of jaw members coupled to the handles by a latching mechanism having two transversely slidable latch members. In one position, the latch members are positioned to allow one handle member to be coupled to one jaw member and the other handle to be coupled to the other jaw member. Upon transversely sliding the latch members to a second position, the one handle is coupled to the other jaw member and the other handle is coupled to the one jaw member. While the construction of the referenced patent has enjoyed great success, it is relatively complex and it contains numerous parts which must be properly assembled and aligned during operation to provide proper functioning.
In a substantially different construction, a plier is provided whereby separate pairs of jaws and handles are pivotally interconnected about a common axis and are arranged such that a pair of movable pins is adapted to alternately engage the jaw and handle pairs to shift the jaw and handle interconnections from an internal position to an external position and visa versa.
An additional form of plier construction provides interconnected levers having two jaw members for simultaneous operation of the tool on internal and external retaining rings by a pair of jaws positioned for internal operation and a pair of jaws for external operation.
Another convertible plier construction utilizes linkages that must be disengaged and the tool reassembled in order to change the relationship between the handles and jaws. Such a construction is cumbersome to use as it requires unneeded preparation time prior to use, and may alter the configuration of the tool such that it becomes uncomfortable to use. In addition at least some such tools have significantly different mechanical advantages in the internal and external positions.
A proposed tool provided handles which were intended to be relatively moveable between internal and external positions. To accomplish this one lever included a U-shaped slot and the other carried a pivot which projected through the slot. Presumably the levers can be moved from a crossed internal ring relationship with the pivot at one end of the slot to a side by side external ring relationship. If the proposed tool was operable at all, it lacked structure to maintain the levers in a selected relationship when in use.